ANATOMY AND PHYSIOLOGY OF THE FOOT OF THE HORSE. 377 
assume the form of papillae ; this, however, is entirely wanting on 
the sensible laminae, which, as has been before observed, are per- 
fectly smooth and glassy. 
The best proof that I can offer in favour of my opinion is, that 
state of parts so gradual in making its appearance, but at the same 
time so certain after an unfavourable termination of a case of lami- 
nitis, the inflammatory action produces a separation of the one 
order of laminae from the other. The sensible laminae now take on 
an abnormal action, that of secreting a peculiar plastic material. 
This material being thrown out from the inferior parts as well as 
the superior, an accumulation must, of necessity, take place at the 
inferior part, and, consequently, the wall is forced forward at the 
inferior part of it, and the os pedis is forced backwards, and thus 
produces convex soles. 
When the sensible laminae have, by any operation or accident, 
been deprived of their natural defence — the insensible laminae — we 
find that they have the property of secreting, and that too in a very 
short space of time, a material which to all appearance is horn, and 
which sufficiently protects them from injury until their proper co- 
vering is grown from above. This, I should say, is only another 
proof of the wise provisions of nature, and is conclusive of the 
normal function of these parts. I have invariably noticed that this 
same substance makes its appearance on the sole after the removal 
of the horny parts, previous to the appearance of the natural fibrous 
protection. A provision of this kind also takes place when the 
bones of the cranium are removed, either from injury or by the 
trephine. Bone itself is never found to be reproduced, but a carti- 
laginous mass soon fills up the chasm, and affords a very great 
defence to the parts beneath. 
The great vascularity of the sensible laminae has led some 
persons more particularly to ascribe to them the property of 
secreting the insensible laminae and inner table of the wall ; but al- 
though, to a casual observer, they would appear the most vascular 
part of the foot, yet investigation will tell us they are least vas- 
cular of all. Their vascular appearance is in a great measure de- 
pendent on their being denuded of any description of protective 
covering when the laminae are removed. Unlike the other surfaces, 
the constant pressure to which they are exposed will also go a great 
way in accounting even for the blood that is found in them ; for this 
pressure greatly facilitates absorption, and, where the absorption is 
going on vigorously, we must have a corresponding deposition, in 
order that an equilibrium may be maintained. The lateral laminal 
arteries, although of some magnitude, have another office to per- 
form besides that of supplying the sensible laminae, for the circulus 
arteriosus in itself is not at all equal to the supply of blood wanted 
VOL. XVIII. 3 F 
